Model organisms
A model organism is a species that is extensively studied to understand particular biological and psychological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. This is possible because fundamental biological principles such as metabolic, regulatory, and developmental pathways, and the genes that code for them, are conserved through evolution. Often, model organisms are chosen on the basis that they are amenable to experimental manipulation. This usually will include characteristics such as; short life-cycle, techniques for genetic manipulation (inbred strains, stem cell lines, and transfection systems), and non-specialist living requirements. Sometimes, the genome arrangement facilitates the sequencing of the model organism's genome, for example, by being very compact or having a low proportion of junk DNA. When researchers look for an organism to use in their studies, they look for several traits. Common among these are size, generation time, accessibility, manipulation, genetics, conservation of mechanisms, and potential economic benefit. As comparative molecular biology has become more common, some researchers have sought model organisms that represent assorted lineages of life. Important model organisms in psychology Invertebrates :* Arbacia punctulata, the purple-spined sea urchin, classical subject of embryological studies :* Caenorhabditis elegans, a nematode, usually called C. elegans Riddle, Donald L.; Blumenthal, Thomas; Meyer, Barbara J.; and Priess, James R. (Eds.). (1997). C. ELEGANS II. Woodbury, NY: Cold Spring Harbor Press. ISBN 0-87969-532-3. Full text available on-line. - an excellent model for understanding the genetic control of development and physiology. C. elegans was the first multicellular organism whose genome was completely sequenced :* Drosophila, usually the species Drosophila melanogaster - a kind of fruit fly, famous as the subject of genetics experiments by Thomas Hunt Morgan and others. Easily raised in lab, rapid generations, mutations easily induced, many observable mutations. Recently, Drosophila has been used for neuropharmacological research . (Molecular genetics, Population genetics, Developmental biology). :* Euprymna scolopes, the Hawaiian bobtail squid, model for animal-bacterial symbiosis, bioluminescent vibrios. :*''Hydra, a Cnidaria, is the model organism to understand the evolution of bilaterian body plans. :* ''Loligo pealei, a squid, subject of studies of nerve function because of its giant axon (nearly 1 mm diameter, roughly a thousand times larger than typical mammalian axons) :* Stomatogastric ganglion, arthropods digestive systems are a model for motor pattern generation seen in all repetitive motions :* Tribolium castaneum, the flour beetle - a small, easily kept darkling beetle used especially in behavioural ecology experiments. Vertebrates *Primates ** Bonobo ** Chimpanzee ** Macaque :* [[Dog|Dog (Canis lupus familiaris)]] - an important respiratory and cardiovascular model :* Cavius porcellus, the guinea pig :* Lamprey :* Mouse (Mus musculus) - the classic model vertebrate. Many inbred strains exist, as well as lines selected for particular traits, often of medical interest, e.g. body size, obesity, muscularity. (Quantitative genetics, Molecular evolution, Genomics) :* Takifugu rubipres, a pufferfish - has a small genome with little junk DNA :*''Oryzias latipes, Medaka (the Japanese ricefish) is an important model in developmental biology, and has the advantage of being much sturdier than the traditional Zebrafish. :* Rat (Rattus norvegicus) - particularly useful as a toxicology model; also particularly useful as a neurological model and source of primary cell cultures, owing to the larger size of organs and suborganellar structures relative to the mouse. ''(Molecular evolution, Genomics)' :* ''Xenopus laevis, the African clawed toad, also used in development because of its large cells, esp. egg cells. :* [[Brachydanio rerio|Zebrafish (Brachydanio rerio)]], a freshwater fish, has a nearly transparent body which provides unique visual access to the animal's internal anatomy throughout its life. Zebrafish are used to study development, toxicology and toxicopathologySpitsbergen J.M. and Kent M.L. (2003). The state of the art of the zebrafish model for toxicology and toxicologic pathology research--advantages and current limitations. Toxicol Pathol. 31 (Supplement), 62-87. PubMed Abstract Link => PMID 12597434., specific gene function and roles of signaling pathways. Model organisms used for specific research objectives Sexual selection and sexual conflict *''Callusobruchus maculatus, the bruchid beetle *Chorthippus parallelus, the meadow grasshopper *Coelopidae - seaweed flies *Diopsidae - stalk-eyed flies *Drosophila'' spp. - fruit flies *''Gryllus bimaculatus, the field cricket *Scathofaga stercoraria, the yellow dung fly Hybrid zones *Bombina bombina'' and variegata *''Podisma'' spp. in the Alps See also * Animal model * Commensalism * Conditional gene knockout * Ensembl genome database of model organisms * Gene knockout * Gene knockdown * Gene knockin * Germline * Gene silencing * Knockout mouse * Recombineering References External links * Wellcome Trust description of model organisms * WWW Virtual Library guide to several model organism resource lists * The Generic Model Organism Database project Category:Model organisms Category:Animal experimentation